Help On Column Tank Lighting

[CaBur]

I have a Marineland 47 Gallon Column Style Aquarium that measures about 20"L x 18"W x 30"H. I have live plants and the light that the tank came with is very under powered. Could someone please suggest a light that could fit (under 18" long) and is powerful enough for my tank? Everything I have found is either too big or too small and under powered. My last resort is to get a light that is too big for the tank, which will look kind of award. Please help.